Coseismic deformation field of the M=6.7 Northridge, California Earthquake of January 17, 1994 recorded by two radar satellites using interferometry

Abstract

Interferometric combination of pairs of synthetic aperture radar (SAR) images acquired by the ERS‐1 and JERS‐1 satellites before and after the Northridge, California earthquake of January 17, 1994 provide two maps of the coseismic deformation field. The fringes corresponding to contours of equal change in satellite‐to‐ground distance show the coseismic displacement of the mainshock. The fringe patterns remain clear for over a year, even in urban areas with structural damage. Elastic dislocation fault models fitting the two radar interferograms are substantially equivalent despite the different radar wavelengths, 56 and 235 mm, for ERS‐1 and JERS‐1, respectively. A single‐fault model based on surveying measurements using the Global Positioning System (GPS) fails to account for parts of the fringe patterns observed by radar satellite, particularly the effects of several aftershocks and localized ground motion.